Thermoplastic resin composition

ABSTRACT

Provided is a thermoplastic resin composition which includes: a first graft copolymer including a C 4  to C 10  alkyl (meth)acrylate-based monomer unit, a C 1  to C 3  alkyl-substituted styrene-based monomer unit, and a vinyl cyan-based monomer unit; a second graft copolymer including a C 4  to C 10  alkyl (meth)acrylate-based monomer unit, an alkyl-unsubstituted styrene-based monomer unit, and a vinyl cyan-based monomer unit; a first styrene-based copolymer including a C 1  to C 3  alkyl-substituted styrene-based monomer unit and a vinyl cyan-based monomer unit; a second styrene-based copolymer including an alkyl-unsubstituted styrene-based monomer unit and a vinyl cyan-based monomer unit; and an olefin-based copolymer including a C 1  to C 3  alkyl (meth)acrylate-based monomer unit. The thermoplastic resin composition exhibits remarkably excellent chemical resistance and remarkably excellent appearance characteristics while maintaining basic properties.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a National Phase of International Application No.PCT/KR2019/014261, which claims priority to and the benefit of KoreanPatent Application No. 10-2018-0132191, filed on Oct. 31, 2018, thedisclosures of which are incorporated herein by reference in theirentirety.

TECHNICAL FIELD

The present invention relates to a thermoplastic resin composition,specifically, a thermoplastic resin composition exhibiting excellentchemical resistance and excellent appearance characteristics.

BACKGROUND ART

Generally, an acrylic-based graft copolymer formed by graftpolymerization of an acrylic-based rubber polymer with an aromaticvinyl-based monomer and a vinyl cyan-based monomer exhibits excellentweather resistance and excellent aging resistance. A thermoplastic resincomposition including such an acrylic-based graft copolymer is used invarious fields such as automobiles, ships, leisure products, buildingmaterials, horticultural products, and the like, and the usage thereofis rapidly increasing.

Meanwhile, with an increased need of a user for emotional quality,research to realize a classy appearance, excellent colorability, andexcellent weather resistance by finishing base materials such as PVC,steel sheets, and the like with the thermoplastic resin composition hasbeen conducted.

Since a decorative sheet including an acrylic-based graft copolymerexhibits excellent processing stability compared to conventional PVC orPP and does not include a heavy metal component, it has attractedattention as an environmentally friendly material. However, thedecorative sheet has a problem in which pressure marks are left duringthe storage process or the dimensions of the sheet are deformed(expanded or reduced) during processing. In addition, when an adhesiveis used for adhesion to the base material, the decorative sheet may bedissolved due to poor chemical resistance.

Therefore, there is a need to develop a thermoplastic resin compositionexhibiting improved appearance quality and improved chemical resistance.

DISCLOSURE Technical Problem

The present invention is directed to providing a thermoplastic resincomposition which exhibits improved chemical resistance, improved heatresistance, and improved appearance characteristics while beingexcellent in basic properties such as processability, hardness,colorability, impact resistance, and the like.

Technical Solution

One aspect of the present invention provides a thermoplastic resincomposition which includes: a first graft copolymer including a C₄ toC₁₀ alkyl (meth)acrylate-based monomer unit, a C₁ to C₃alkyl-substituted styrene-based monomer unit, and a vinyl cyan-basedmonomer unit; a second graft copolymer including a C₄ to C₁₀ alkyl(meth)acrylate-based monomer unit, an alkyl-unsubstituted styrene-basedmonomer unit, and a vinyl cyan-based monomer unit; a first styrene-basedcopolymer including a C₁ to C₃ alkyl-substituted styrene-based monomerunit and a vinyl cyan-based monomer unit; a second styrene-basedcopolymer including an alkyl-unsubstituted styrene-based monomer unitand a vinyl cyan-based monomer unit; and an olefin-based copolymerincluding a C₁ to C₃ alkyl (meth)acrylate-based monomer unit.

Advantageous Effects

A thermoplastic resin composition according to the present invention canexhibit significantly improved chemical resistance, heat resistance, andappearance characteristics while being excellent in basic propertiessuch as processability, hardness, colorability, impact resistance, andthe like.

Modes of the Invention

Hereinafter, the present invention will be described in more detail tofacilitate understanding of the present invention.

Terms and words used in this specification and claims should not beinterpreted as being limited to commonly used meanings or meanings indictionaries, and, based on the principle that the inventors canappropriately define concepts of terms in order to describe theirinvention in the best way, the terms and words should be interpretedwith meanings and concepts which are consistent with the technologicalspirit of the present invention.

In the present invention, the weight-average molecular weight of a shellof a graft copolymer may refer to a weight-average molecular weight of acopolymer including an aromatic vinyl-based monomer unit and a vinylcyan-based monomer unit which are grafted onto a core.

Here, the aromatic vinyl-based monomer unit may be one or more selectedfrom the group consisting of a C₁ to C₃ alkyl-substituted styrene-basedmonomer unit and an alkyl-unsubstituted styrene-based monomer unit.

In the present invention, the weight-average molecular weight of a shellof a graft copolymer may be measured as a relative value with respect toa standard polystyrene (PS) sample by gel permeation chromatography(GPC, Waters Breeze) after the graft copolymer is dissolved in acetoneand centrifuged and the portion (sol) dissolved in acetone is thendissolved in tetrahydrofuran (THF).

In the present invention, the degree of grafting for a graft copolymermay be calculated by the following equation.Degree of grafting (%):Weight(g) of grafted monomers/Weight(g) ofrubber×100

Weight (g) of grafted monomers: Weight of insoluble substance (gel)obtained after graft copolymer powder is dissolved in acetone andcentrifuged

Weight (g) of rubber: Weight of C₄ to C₁₀ alkyl (meth)acrylate-basedmonomer theoretically added in the preparation of graft copolymer powder

In the present invention, the average particle diameters of a seed, acore, and a graft copolymer may be measured by a dynamic lightscattering method, specifically, by using a Nicomp 380 instrument(manufactured by PSS Nicomp).

In the present invention, an average particle diameter may refer to anarithmetic average particle diameter in the particle size distributionas measured by a dynamic light scattering method, specifically, anaverage particle diameter measured in the scattering intensitydistribution.

In the present invention, a weight-average molecular weight may bemeasured as a relative value with respect to a standard PS sample by GPC(Waters Breeze) using THF as an eluate.

1. Thermoplastic Resin Composition

A thermoplastic resin composition according to an embodiment of thepresent invention includes: A-1) a first graft copolymer including a C₄to C₁₀ alkyl (meth)acrylate-based monomer unit, a C₁ to C₃alkyl-substituted styrene-based monomer unit, and a vinyl cyan-basedmonomer unit; A-2) a second graft copolymer including a C₄ to C₁₀ alkyl(meth)acrylate-based monomer unit, an alkyl-unsubstituted styrene-basedmonomer unit, and a vinyl cyan-based monomer unit; B-1) a firststyrene-based copolymer including a C₁ to C₃ alkyl-substitutedstyrene-based monomer unit and a vinyl cyan-based monomer unit; B-2) asecond styrene-based copolymer including an alkyl-unsubstitutedstyrene-based monomer unit and a vinyl cyan-based monomer unit; and C)an olefin-based copolymer including a C₁ to C₃ alkyl(meth)acrylate-based monomer unit.

Hereinafter, each component of the thermoplastic resin compositionaccording to the present invention will be described in detail.

A-1) First Graft Copolymer

The first graft copolymer includes a C₄ to C₁₀ alkyl(meth)acrylate-based monomer unit, a C₁ to C₃ alkyl-substitutedstyrene-based monomer unit, and a vinyl cyan-based monomer unit.

Since the first graft copolymer includes a C₁ to C₃ alkyl-substitutedstyrene-based monomer unit, it may impart remarkably excellent heatresistance and remarkably excellent appearance characteristics to thethermoplastic resin composition. In addition, the first graft copolymermay be uniformly dispersed in the thermoplastic resin composition due tohaving significantly improved compatibility with a first styrene-basedcopolymer to be described below.

In addition, the first graft copolymer may impart excellent impactresistance to the thermoplastic resin composition.

The first graft copolymer may have a core-shell structure including: acore formed of a crosslinked polymer including a C₄ to C₁₀ alkyl(meth)acrylate-based monomer unit; and a shell including analkyl-substituted styrene-based monomer unit and a vinyl cyan-basedmonomer unit which are grafted onto the core.

The C₄ to C₁₀ alkyl (meth)acrylate-based monomer unit may be a unitderived from a C₄ to C₁₀ alkyl (meth)acrylate-based monomer.

The C₄ to C₁₀ alkyl (meth)acrylate-based monomer may be one or moreselected from the group consisting of butyl (meth)acrylate, pentyl(meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, octyl(meth)acrylate, 2-ethylhexyl (meth)acrylate, nonyl (meth)acrylate,isononyl (meth)acrylate, and decyl (meth)acrylate, with butyl acrylatebeing preferred.

The C₄ to C₁₀ alkyl (meth)acrylate-based monomer unit may be included inan amount of 40 to 60 wt % or 45 to 55 wt % with respect to the totalweight of the first graft copolymer, with the range of 45 to 55 wt %being preferred. When the above-described range is satisfied, the impactresistance of the first graft copolymer can be improved.

The C₁ to C₃ alkyl-substituted styrene-based monomer unit may be a unitderived from a C₁ to C₃ alkyl-substituted styrene-based monomer.

The C₁ to C₃ alkyl-substituted styrene-based monomer may be one or moreselected from the group consisting of α-methylstyrene, p-methylstyrene,and 2,4-dimethylstyrene, with α-methylstyrene being preferred.

The C₁ to C₃ alkyl-substituted styrene-based monomer unit may beincluded in an amount of 25 to 45 wt % or 30 to 40 wt % with respect tothe total weight of the first graft copolymer, with the range of 30 to40 wt % being preferred. When the above-described range is satisfied,the heat resistance, appearance characteristics, and impact resistanceof the thermoplastic resin composition can be improved.

The vinyl cyan-based monomer unit may be a unit derived from a vinylcyan-based monomer.

The vinyl cyan-based monomer may be one or more selected from the groupconsisting of acrylonitrile, methacrylonitrile, and ethacrylonitrile,with acrylonitrile being preferred.

The vinyl cyan-based monomer unit may be included in an amount of 5 to25 wt % or 10 to 20 wt % with respect to the total weight of the firstgraft copolymer, with the range of 10 to 20 wt % being preferred. Whenthe above-described range is satisfied, the chemical resistance of thefirst graft copolymer can be improved.

The first graft copolymer may further include an alkyl-unsubstitutedstyrene-based monomer unit to facilitate polymerization. Thealkyl-unsubstituted styrene-based monomer unit may be a unit derivedfrom an alkyl-unsubstituted styrene-based monomer. Thealkyl-unsubstituted styrene-based monomer may be one or more selectedfrom the group consisting of styrene, p-bromostyrene, o-bromostyrene,and p-chlorostyrene, with styrene being preferred.

The alkyl-unsubstituted styrene-based monomer unit may be included in anamount of 0.1 to 15 wt % or 1 to 10 wt % with respect to the totalweight of the first graft copolymer, with the range of 1 to 10 wt %being preferred. When the above-described range is satisfied,polymerization of the first graft copolymer can more easily proceed.

The core of the first graft copolymer may have an average particlediameter different from that of the second graft copolymer, andspecifically, the core of the first graft copolymer may have an averageparticle diameter greater than that of the second graft copolymer.

Since the thermoplastic resin composition includes at least two types ofgraft copolymers having cores having mutually different average particlediameters, all of impact resistance, weather resistance, colorability,surface gloss characteristics, and appearance characteristics can beimproved.

The core of the first graft copolymer may have an average particlediameter of 300 to 500 nm or 350 to 450 nm, with the range of 350 to 450nm being preferred. When the above-described range is satisfied, theimpact resistance and surface gloss characteristics of the thermoplasticresin composition can be improved. Below the above-described range, theimpact resistance of the thermoplastic resin composition may bedegraded, and above the above-described range, the surface glosscharacteristics thereof may be degraded.

The first graft copolymer may have a degree of grafting of 20 to 100%,40 to 80%, or 45 to 60%, with the range of 40 to 60% being preferred.When the above-described range is satisfied, the impact resistance anddispersibility of the thermoplastic resin composition can be improved.

The shell of the first graft copolymer may have a weight-averagemolecular weight of 100,000 to 300,000 g/mol or 150,000 to 250,000g/mol, with the range of 150,000 to 250,000 g/mol being preferred. Whenthe above-described range is satisfied, the impact resistance of thethermoplastic resin composition can be improved.

The first graft copolymer may be selected from the group consisting of abutyl acrylate/α-methylstyrene/acrylonitrile copolymer and a butylacrylate/styrene/α-methylstyrene/acrylonitrile copolymer, with the butylacrylate/styrene/α-methylstyrene/acrylonitrilecopolymerbeingpreferred.

The first graft copolymer may be included in an amount of 5 to 30 partsby weight, 10 to 25 parts by weight, or 10 to 15 parts by weight withrespect to 100 parts by weight of the sum of the first graft copolymer,the second graft copolymer, the first styrene-based copolymer, and thesecond styrene-based copolymer, with the range of 10 to 15 parts byweight being preferred. When the above-described range is satisfied, theimpact resistance of the thermoplastic resin composition can besignificantly improved. Below the above-described range, the impactresistance and appearance characteristics of the thermoplastic resincomposition may be significantly degraded, and above the above-describedrange, the appearance characteristics thereof may be significantlydegraded.

Meanwhile, the first graft copolymer may be prepared by a methodincluding the steps of: 1) preparing a core by polymerizing one or moreselected from the group consisting of a C₄ to C₁₀ alkyl(meth)acrylate-based monomer, a C₁ to C₃ alkyl-substituted styrene-basedmonomer, an alkyl-unsubstituted styrene-based monomer, and a vinylcyan-based monomer; and 2) in the presence of the core, preparing ashell by polymerizing a C₁ to C₃ alkyl-substituted styrene-based monomerand a vinyl cyan-based monomer.

The step—of preparing a core may include the steps of: preparing a seedby polymerizing one or more selected from the group consisting of a C₄to C₁₀ alkyl (meth)acrylate-based monomer, a C₁ to C₃ alkyl-substitutedstyrene-based monomer, an alkyl-unsubstituted styrene-based monomer, anda vinyl cyan-based monomer; and, in the presence of the seed, preparinga core by polymerizing a C₄ to C₁₀ alkyl (meth)acrylate-based monomer.

The preparation of a seed and a core may be performed in the presence ofone or more selected from the group consisting of an emulsifier, aninitiator, a crosslinking agent, a grafting agent, an electrolyte, andwater.

The emulsifier may be one or more selected from the group consisting ofmetal salt derivatives of a C₁₂ to Cis alkyl sulfosuccinic acid andmetal salt derivatives of a C₁₂ to C₂₀ alkyl sulfuric acid ester.

The metal salt derivative of a C₁₂ to Cis alkyl sulfosuccinic acid maybe one or more selected from the group consisting of dicyclohexyl sodiumsulfosuccinate, dihexyl sodium sulfosuccinate, di-2-ethylhexyl sodiumsulfosuccinate, di-2-ethylhexyl potassium sulfosuccinate, anddi-2-ethylhexyl lithium sulfosuccinate.

The metal salt derivative of a C₁₂ to C₂₀ alkyl sulfuric acid ester maybe one or more selected from the group consisting of sodium dodecylsulfate, sodium dodecylbenzenesulfate, sodium octadecyl sulfate, sodiumoleic sulfate, potassium dodecyl sulfate, and potassium octadecylsulfate.

The initiator may be an inorganic peroxide or an organic peroxide. Theinorganic peroxide is a water-soluble initiator and may be one or moreselected from the group consisting of potassium persulfate, sodiumpersulfate, and ammonium persulfate. The organic peroxide is afat-soluble initiator and may be one or more selected from the groupconsisting of cumene hydroperoxide and benzoyl peroxide.

The crosslinking agent may be one or more selected from the groupconsisting of ethylene glycol dimethacrylate, diethylene glycoldimethacrylate, triethylene glycol dimethacrylate, 1,3-butanedioldimethacrylate, 1,6-hexanediol dimethacrylate, neopentyl glycoldimethacrylate, trimethylolpropane trimethacrylate, andtrimethylolmethane triacrylate.

The grafting agent may be one or more selected from the group consistingof allyl methacrylate, triallyl isocyanurate, triallylamine, anddiallylamine.

The electrolyte may be one or more selected from the group consisting ofKCl, NaCl, KHCO₃, NaHCO₃, K₂CO₃, Na₂CO₃, KHSO₃, NaHSO₄, Na₂S₂O₇, K₄P₂O₇,K₃PO₄, Na₃PO₄ or Na₂HPO₄, KOH, and NaOH, with KOH being preferred.

The water serves as a medium in emulsion polymerization and may be ionexchanged water.

Meanwhile, in the preparation of a shell, a C₁ to C₃ alkyl-substitutedstyrene-based monomer and a vinyl cyan-based monomer may be polymerizedwhile being continuously added at a predetermined rate. When the C₁ toC₃ alkyl-substituted styrene-based monomer and the vinyl cyan-basedmonomer are added by the above-described method, heat can be controlledand a runaway reaction caused by excessive release of heat can be easilysuppressed during polymerization.

The polymerization may be emulsion polymerization and may be performedat 50 to 85° C. or 60 to 80° C., with the range of 60 to 80° C. beingpreferred. When the above-described range is satisfied, emulsionpolymerization can be stably performed.

The preparation of a shell may be performed in the presence of one ormore selected from the group consisting of an emulsifier, an initiator,and water.

It is preferable that the polymerization is performed while theemulsifier, initiator, and water are continuously added together withthe styrene-based monomer and the vinyl cyan-based monomer. When theabove-described condition is satisfied, a constant pH can be maintainedto facilitate graft polymerization, and a graft copolymer whoseparticles have not only excellent stability but also a uniform internalstructure can be prepared.

The emulsifier may be a metal salt derivative of a carboxylic acid, andthe metal salt derivative of a carboxylic acid may be one or moreselected from the group consisting of metal salts of a C₁₂ to C₂₀ fattyacid and metal salts of rosin acid.

The metal salt of a C₁₂ to C₂₀ fatty acid may be one or more selectedfrom the group consisting of sodium salts of a fatty acid, sodiumlaurate, sodium oleate, and potassium oleate.

The metal salt of rosin acid may be one or more selected from the groupconsisting of sodium rosinate and potassium rosinate.

Types of the initiator have been described above, with the organicperoxide being preferred, and t-butylperoxy ethylhexyl carbonate beingmore preferred.

Meanwhile, the graft copolymer prepared by the above-described methodmay be a latex form.

The graft copolymer in latex form may be subjected to coagulation,aging, washing, dehydration, and drying to form a graft copolymer inpowder form.

A-2) Second Graft Copolymer

The second graft copolymer includes a C₄ to C₁₀ alkyl(meth)acrylate-based monomer unit, an alkyl-unsubstituted styrene-basedmonomer unit, and a vinyl cyan-based monomer unit.

The second graft copolymer may impart excellent weather resistance,colorability, impact resistance, chemical resistance, and surface glosscharacteristics to the thermoplastic resin composition.

In addition, since the second graft copolymer includes analkyl-unsubstituted styrene-based monomer unit, it may be uniformlydispersed in the thermoplastic resin composition due to havingsignificantly improved compatibility with a second styrene-basedcopolymer to be described below.

The second graft copolymer may have a core-shell structure including: acore formed of a crosslinked polymer including one or more selected fromthe group consisting of a C₄ to C₁₀ alkyl (meth)acrylate-based monomerunit, an alkyl-unsubstituted styrene-based monomer unit, and a vinylcyan-based monomer unit; and a shell including an alkyl-unsubstitutedstyrene-based monomer unit and a vinyl cyan-based monomer unit which aregrafted onto the core.

The C₄ to C₁₀ alkyl (meth)acrylate-based monomer unit may be included inan amount of 40 to 60 wt % or 45 to 55 wt % with respect to the totalweight of the second graft copolymer, with the range of 45 to 55 wt %being preferred. When the above-described range is satisfied, theweather resistance and impact resistance of the second graft copolymercan be improved.

The alkyl-unsubstituted styrene-based monomer unit may be included in anamount of 25 to 45 wt % or 30 to 40 wt % with respect to the totalweight of the second graft copolymer, with the range of 30 to 40 wt %being preferred. When the above-described range is satisfied, theprocessability and impact resistance of the second graft copolymer canbe improved.

The vinyl cyan-based monomer unit may be included in an amount of 5 to25 wt % or 10 to 20 wt % with respect to the total weight of the secondgraft copolymer, with the range of 10 to 20 wt % being preferred. Whenthe above-described range is satisfied, the chemical resistance of thesecond graft copolymer can be improved.

The descriptions of the C₄ to C₁₀ alkyl-unsubstituted styrene-basedmonomer unit, the alkyl-unsubstituted styrene-based monomer unit, andthe vinyl cyan-based monomer unit have been described above.

The core of the second graft copolymer may have an average particlediameter of 50 to 150 nm or 75 to 125 nm, with the range of 75 to 125 nmbeing preferred. When the above-described range is satisfied, thespecific surface area of the core in the thermoplastic resin compositionis increased to significantly improve weather resistance, and visiblelight can penetrate without being scattered in the core to significantlyimprove colorability. In addition, the chemical resistance, appearancecharacteristics, and surface gloss characteristics of the thermoplasticresin composition can be improved. Below the above-described range, theweather resistance, chemical resistance, appearance characteristics, andsurface gloss characteristics of the thermoplastic resin composition maybe significantly degraded, and above the above-described range, theweather resistance and colorability thereof may be significantlydegraded.

The second graft copolymer may have a degree of grafting of 20 to 80% or25 to 60%, with the range of 25 to 60% being preferred. When theabove-described range is satisfied, a second graft copolymer exhibitingexcellent colorability, excellent dispersibility, and excellent surfacegloss characteristics can be prepared.

The shell of the second graft copolymer may have a weight-averagemolecular weight of 50,000 to 200,000 g/mol or 70,000 to 170,000 g/mol,with the range of 70,000 to 170,000 g/mol being preferred. When theabove-described range is satisfied, a second graft copolymer exhibitingexcellent dispersibility and excellent mechanical properties can beprepared.

The second graft copolymer may be a butyl acrylate/styrene/acrylonitrilecopolymer.

The second graft copolymer may be included in an amount of 0.1 to 15parts by weight, 1 to 10 parts by weight, or 5 to 8 parts by weight withrespect to 100 parts by weight of the sum of the first graft copolymer,the second graft copolymer, the first styrene-based copolymer, and thesecond styrene-based copolymer, with the range of 5 to 8 parts by weightbeing preferred. When the above-described range is satisfied, theweather resistance, chemical resistance, colorability, appearancecharacteristics, and surface gloss characteristics of the thermoplasticresin composition can be significantly improved. Below theabove-described range, the appearance characteristics, weatherresistance, and colorability of the thermoplastic resin composition maybe degraded, and above the above-described range, the impact resistanceof the thermoplastic resin composition may be degraded.

Meanwhile, the second graft copolymer may be prepared by a methodincluding the steps of: 1) preparing a core by polymerizing one or moreselected from the group consisting of a C₄ to C₁₀ alkyl(meth)acrylate-based monomer, an alkyl-unsubstituted styrene-basedmonomer, and a vinyl cyan-based monomer; and 2) in the presence of thecore, preparing a shell by polymerizing an alkyl-unsubstitutedstyrene-based monomer and a vinyl cyan-based monomer.

The step of preparing a core may include the steps of: preparing a seedby polymerizing one or more selected from the group consisting of a C₄to C₁₀ alkyl (meth)acrylate-based monomer, an alkyl-unsubstitutedstyrene-based monomer, and a vinyl cyan-based monomer; and, in thepresence of the seed, preparing a core by polymerizing a C₄ to C₁₀ alkyl(meth)acrylate-based monomer.

Other descriptions of the preparation method of the second graftcopolymer have been given in the preparation method of the first graftcopolymer.

Meanwhile, in the present invention, the sum of the content of the firstgraft copolymer and the content of the second graft copolymer may be 10to 35 parts by weight, preferably, 15 to 30 parts by weight with respectto 100 parts by weight of the sum of the first graft copolymer, thesecond graft copolymer, the first styrene-based copolymer, and thesecond styrene-based copolymer. When the above-described range issatisfied, the thermoplastic resin composition can attain excellentimpact resistance, excellent appearance characteristics, and excellenthardness. Below the above-described range, the impact resistance of thethermoplastic resin composition may be significantly degraded, and abovethe above-described range, a melt flow index may be lowered, andappearance characteristics may be significantly degraded.

In addition, in the present invention, a weight ratio of the first graftcopolymer and the second graft copolymer may be 1.5:1 to 10:1,preferably 1.5:1 to 5:1, and more preferably 1.5:1 to 3:1. When theabove-described range is satisfied, the impact resistance and appearancecharacteristics of the thermoplastic resin composition can be improved.Below the above-described range, the impact resistance of thethermoplastic resin composition may be degraded, and above theabove-described range, the appearance characteristics of thethermoplastic resin composition may be degraded.

B-1) First Styrene-Based Copolymer

The first styrene-based copolymer is a matrix copolymer and includes aC₁ to C₃ alkyl-substituted styrene-based monomer unit and a vinylcyan-based monomer unit.

The first styrene-based copolymer may impart excellent heat resistanceand excellent appearance characteristics to the thermoplastic resincomposition. Specifically, excellent heat resistance can provideimproved dimensional stability of a molded article formed of thethermoplastic resin composition and minimized pressure marks.

In addition, since the first styrene-based copolymer includes a C₁ to C₃alkyl-substituted styrene-based monomer unit, it may be highlycompatible with the first graft copolymer.

Types of the C₁ to C₃ alkyl-substituted styrene-based monomer unit andthe vinyl cyan-based monomer unit have been described above.

The first styrene-based copolymer may be a copolymer of a monomermixture including a C₁ to C₃ alkyl-substituted styrene-based monomer anda vinyl cyan-based monomer.

The monomer mixture may include a C₁ to C₃ alkyl-substitutedstyrene-based monomer and a vinyl cyan-based monomer in a weight ratioof 60:40 to 90:10 or 65:35 to 85:15, with the range of 65:35 to 85:15being preferred. When the above-described range is satisfied, heatresistance can be improved.

The first styrene-based copolymer may further include analkyl-unsubstituted styrene-based monomer unit to facilitatepolymerization.

That is, the first styrene-based copolymer may be a copolymer of amonomer mixture including a C₁ to C₃ alkyl-substituted styrene-basedmonomer, a vinyl cyan-based monomer, and an alkyl-unsubstitutedstyrene-based monomer. Types of the alkyl-unsubstituted styrene-basedmonomer unit have been described above.

In this case, the monomer mixture may include the C₁ to C₃alkyl-substituted styrene-based monomer at 55 to 75 wt %, the vinylcyan-based monomer at 20 to 40 wt %, and the alkyl-unsubstitutedstyrene-based monomer at 0.1 to 15 wt %, and preferably includes the C₁to C₃ alkyl-substituted styrene-based monomer at 60 to 70 wt %, thevinyl cyan-based monomer at 25 to 35 wt %, and the alkyl-unsubstitutedstyrene-based monomer at 1 to 10 wt %. When the above-described range issatisfied, polymerization of the first styrene-based copolymer can moreeasily proceed.

The first styrene-based copolymer may have a weight-average molecularweight of 50,000 to 150,000 g/mol or 70,000 to 130,000 g/mol, with therange of 70,000 to 130,000 g/mol being preferred. When theabove-described range is satisfied, excellent chemical resistance andmechanical properties can be realized. Below the above-described range,the mechanical properties of the thermoplastic resin composition may bedegraded. Above the above-described range, processability may bedegraded.

The first styrene-based copolymer may be selected from the groupconsisting of an α-methylstyrene/acrylonitrile copolymer and anα-methylstyrene/styrene/acrylonitrile copolymer, with theα-methylstyrene/acrylonitrile copolymer being preferred.

The first styrene-based copolymer may be included in an amount of 2 to25 parts by weight, 7 to 20 parts by weight, 14 to 20 parts by weight,or 14 to 16 parts by weight with respect to 100 parts by weight of thesum of the first graft copolymer, the second graft copolymer, the firststyrene-based copolymer, and the second styrene-based copolymer, withthe range of 14 to 16 parts by weight being preferred. When theabove-described range is satisfied, the heat resistance, processability,and appearance characteristics of the thermoplastic resin compositioncan be improved. Specifically, below the above-described range, the heatresistance of the thermoplastic resin composition is degraded, and thusappearance characteristics may be degraded. Above the above-describedrange, processability and chemical resistance may be degraded.

The first styrene-based copolymer may be a copolymer prepared bysuspension polymerization or bulk polymerization of a monomer mixtureincluding a C₁ to C₃ alkyl-substituted styrene-based monomer and a vinylcyan-based monomer, with the copolymer prepared by bulk polymerizationcapable of preparing a high-purity polymer being preferred.

B-2) Second Styrene-Based Copolymer

The second styrene-based copolymer is a matrix copolymer and includes analkyl-unsubstituted styrene-based monomer unit and a vinyl cyan-basedmonomer unit.

The second styrene-based copolymer may impart excellent processability,chemical resistance, and mechanical properties to the thermoplasticresin composition. Since the second styrene-based copolymer includes analkyl-unsubstituted styrene-based monomer unit, it may have improvedcompatibility with the second graft copolymer and thus may allow thesecond graft copolymer to be uniformly dispersed in the thermoplasticresin composition.

Types of the alkyl-unsubstituted styrene-based monomer unit and thevinyl cyan-based monomer unit have been described above.

The second styrene-based copolymer may be a copolymer of a monomermixture including an alkyl-unsubstituted styrene-based monomer and avinyl cyan-based monomer.

The monomer mixture may include an alkyl-unsubstituted styrene-basedmonomer and a vinyl cyan-based monomer in a weight ratio of 60:40 to90:10 or 65:35 to 85:15, with the range of 65:35 to 85:15 beingpreferred. When the above-described range is satisfied, processabilityand chemical resistance can be improved.

The second styrene-based copolymer may have a weight-average molecularweight of 100,000 to 250,000 g/mol or 130,000 to 220,000 g/mol, with therange of 130,000 to 220,000 g/mol being preferred. When theabove-described range is satisfied, excellent chemical resistance andexcellent mechanical properties can be realized. Below theabove-described range, the mechanical properties of the thermoplasticresin composition may be degraded, and above the above-described range,the processability of the thermoplastic resin composition may bedegraded.

It is preferable that the second styrene-based copolymer is astyrene/acrylonitrile copolymer.

The second styrene-based copolymer may be included in an amount of 50 to80 parts by weight, 55 to 75 parts by weight, or 62 to 66 parts byweight with respect to 100 parts by weight of the sum of the first graftcopolymer, the second graft copolymer, the first styrene-basedcopolymer, and the second styrene-based copolymer, with the range of 62to 66 parts by weight being preferred. When the above-described range issatisfied, the processability, chemical resistance, and mechanicalproperties of the thermoplastic resin composition can be improved. Belowthe above-described range, the chemical resistance and processability ofthe thermoplastic resin composition may be degraded, and above theabove-described range, the mechanical properties of the thermoplasticresin composition may be degraded.

The second styrene-based copolymer may be a copolymer prepared bysuspension polymerization or bulk polymerization of analkyl-unsubstituted styrene-based monomer and a vinyl cyan-basedmonomer, with the copolymer prepared by bulk polymerization capable ofpreparing a high-purity copolymer being preferred.

Meanwhile, in the present invention, the sum of the content of the firststyrene-based copolymer and the content of the second styrene-basedcopolymer may be 65 to 90 parts by weight, preferably, 70 to 85 parts byweight with respect to 100 parts by weight of the sum of the first graftcopolymer, the second graft copolymer, the first styrene-basedcopolymer, and the second styrene-based copolymer. Below theabove-described range, the processability of the thermoplastic resincomposition may be degraded, and above the above-described range, theimpact resistance of the thermoplastic resin composition may bedegraded.

C) Olefin-Based Copolymer

The olefin-based copolymer is an additive and includes a C₁ to C₃ alkyl(meth)acrylate-based monomer unit.

The olefin-based copolymer may impart excellent chemical resistance tothe thermoplastic resin composition.

The olefin-based copolymer may be a copolymer of a monomer mixtureincluding a C₂ to C₄ olefin-based monomer and a C₁ to C₃ alkyl(meth)acrylate-based monomer.

The C₂ to C₄ olefin-based monomer may be one or more selected from thegroup consisting of ethylene, propylene, and butene, with ethylene beingpreferred.

The C₁ to C₃ alkyl (meth)acrylate-based monomer may be one or moreselected from the group consisting of methyl (meth)acrylate, ethyl(meth)acrylate, and propyl (meth)acrylate, with methyl acrylate beingpreferred.

The olefin-based copolymer may include a C₂ to C₄ olefin-based monomerunit and a C₁ to C₃ alkyl (meth)acrylate-based monomer unit in a weightratio of 85:15 to 65:35 or 80:20 to 70:30, with the range of 80:20 to70:30 being preferred. When the above-described range is satisfied, thechemical resistance of the olefin-based copolymer can be improved.Specifically, when the alkyl (meth)acrylate-based monomer unit isinsufficiently included, the compatibility of the olefin-based copolymerwith the first graft copolymer, the second graft copolymer, the firststyrene-based copolymer, and the second styrene-based copolymer isdegraded such that it may not be uniformly dispersed in thethermoplastic resin composition, and thus an effect of improvingchemical resistance may be degraded. When the alkyl (meth)acrylate-basedmonomer unit is excessively included, the compatibility of theolefin-based copolymer with the first graft copolymer, the second graftcopolymer, the first styrene-based copolymer, and the secondstyrene-based copolymer is improved, but the content of an olefin-basedmonomer unit is decreased, and thus an effect of improving chemicalresistance may be degraded.

The olefin-based copolymer may have a weight-average molecular weight of50,000 to 200,000 g/mol, 70,000 to 150,000 g/mol, or 90,000 to 120,000g/mol, with the range of 90,000 to 120,000 g/mol being preferred. Whenthe above-described range is satisfied, the olefin-based copolymerexhibits excellent compatibility with the first graft copolymer, thesecond graft copolymer, the first styrene-based copolymer, and thesecond styrene-based copolymer, and a thermoplastic resin compositionexhibiting excellent mechanical properties can be provided.Specifically, below the above-described range, mechanical properties maybe degraded, and above the above-described range, the compatibility ofthe olefin-based copolymer with the first graft copolymer, the secondgraft copolymer, the first styrene-based copolymer, and the secondstyrene-based copolymer is degraded such that it may not be uniformlydispersed in the thermoplastic resin composition, and thus an effect ofimproving chemical resistance may be degraded.

It is preferable that the olefin-based copolymer is an ethylene/methylacrylate copolymer.

The olefin-based copolymer may be included in an amount of 0.01 to 2parts by weight or 0.5 to 1 part by weight with respect to 100 parts byweight of the sum of the first graft copolymer, the second graftcopolymer, the first styrene-based copolymer, and the secondstyrene-based copolymer in the thermoplastic resin composition, with therange of 0.5 to 1 part by weight being preferred. When theabove-described range is satisfied, the chemical resistance of thethermoplastic resin composition can be improved without adverselyaffecting the hardness, mechanical properties, and heat resistancethereof. Below the above-described range, the chemical resistance of thethermoplastic resin composition may be degraded, and above theabove-described range, the impact resistance of the thermoplastic resincomposition may be degraded.

The olefin-based polymer may be a commercially available product ordirectly prepared.

When the olefin-based polymer is directed prepared, one or morepolymerization methods selected from the group consisting of solutionpolymerization, slurry polymerization, gas-phase polymerization, andhigh-pressure polymerization may be used.

Meanwhile, the thermoplastic resin composition according to anembodiment of the present invention may further include one or moreadditives selected from the group consisting of an anti-dripping agent,a flame retardant, an antibacterial agent, an antistatic agent, astabilizer, a releasing agent, a thermal stabilizer, an UV stabilizer,an inorganic additive, a lubricant, an antioxidant, a photostabilizer, apigment, a dye, and an inorganic filler.

It is preferable that the thermoplastic resin composition according toan embodiment of the present invention includes one or more selectedfrom the group consisting of a lubricant, an antioxidant, and an UVstabilizer.

2. Thermoplastic Resin Molded Article

A thermoplastic resin molded article according to another embodiment ofthe present invention is formed of the thermoplastic resin compositionaccording to an embodiment of the present invention and may have a heatdeflection temperature of 87° C. or more and an impact strength of 6.5kg cm/cm or more. It is preferable that the thermoplastic resin moldedarticle has a heat deflection temperature of 89° C. or more and animpact strength of 6.7 kg cm/cm or more.

When the above-described condition is satisfied, a thermoplastic resinmolded article exhibiting excellent appearance characteristics,excellent heat resistance, and excellent impact resistance can beformed.

The thermoplastic resin molded article according to another embodimentof the present invention may be a sheet, preferably, a decorative sheetfor furniture.

Hereinafter, exemplary embodiments of the present invention will bedescribed in detail so that those of ordinary skill in the art caneasily carry out the present invention. However, it should be understoodthat the present invention can be implemented in various forms, and thatthe exemplary embodiments are not intended to limit the presentinvention thereto.

Preparation Example 1

<Preparation of Seed>

3 parts by weight of styrene, 3 parts by weight of acrylonitrile, 0.1part by weight of sodium dodecyl sulfate as an emulsifier, 0.03 part byweight of ethylene glycol dimethacrylate as a crosslinking agent, 0.02part by weight of allyl methacrylate as a grafting agent, 0.025 part byweight of KOH as an electrolyte, and 53.32 parts by weight of distilledwater were batch-added to a nitrogen-substituted reactor, and thetemperature inside the reactor was raised to 70° C. Afterward, 0.03 partby weight of potassium persulfate as an initiator was batch-added toinitiate polymerization, and the polymerization was performed for 2hours and then terminated, thereby obtaining a seed (average particlediameter: 200 nm).

The average particle diameter of the seed was measured using a Nicomp380 instrument (manufactured by PSS Nicomp) by a dynamic lightscattering method.

<Preparation of Core>

Polymerization was performed for 4 hours while continuously adding, tothe seed-containing reactor, a mixture including 50 parts by weight ofbutyl acrylate, 0.6 part by weight of sodium dodecyl sulfate as anemulsifier, 0.1 part by weight of ethylene glycol dimethacrylate as acrosslinking agent, 0.04 part by weight of allyl methacrylate as agrafting agent, 30 parts by weight of distilled water, and 0.05 part byweight of potassium persulfate as an initiator at 70° C. and apredetermined rate. After the continuous addition was terminated,polymerization was further performed for another 1 hour and thenterminated, thereby obtaining a core (average particle diameter: 400nm).

The average particle diameter of the core was measured using a Nicomp380 instrument (manufactured by PSS Nicomp) by a dynamic lightscattering method.

<Preparation of Shell>

Polymerization was performed for 3 hours while adding, to thecore-containing reactor, 35 parts by weight of α-methylstyrene, 9 partsby weight of acrylonitrile, and 39 parts by weight of distilled waterand continuously adding each of a first mixture including 1.9 parts byweight of potassium rosinate as an emulsifier and 0.19 part by weight oft-butylperoxy ethylhexyl carbonate as an initiator and a second mixtureincluding 0.16 part by weight of sodium pyrophosphate, 0.24 part byweight of dextrose, and 0.004 part by weight of ferrous sulfate asactivators at 75° C. and a predetermined rate. After the continuousaddition was completed, polymerization was further performed at 75° C.for another 1 hour and then terminated by lowering the temperatureinside the reactor to 60° C., thereby preparing a graft copolymer latex(average particle diameter: 500 nm) including a shell.

The average particle diameter of the graft copolymer latex was measuredusing a Nicomp 380 instrument (manufactured by PSS Nicomp) by a dynamiclight scattering method.

<Preparation of Graft Copolymer Powder>

The graft copolymer latex was coagulated at 70° C. and atmosphericpressure for 7 minutes by applying 0.8 part by weight of an aqueouscalcium chloride solution (concentration: 23 wt %) thereto, aged at 93°C. for 7 minutes, dehydrated, washed, and then dried with 90° C. hot airfor 30 minutes, thereby preparing a graft copolymer powder.

Preparation Example 2

<Preparation of Seed>

6 parts by weight of butylacrylate, 0.5 part by weight of sodium dodecylsulfate as an emulsifier, 0.03 part by weight of ethylene glycoldimethacrylate as a crosslinking agent, 0.02 part by weight of allylmethacrylate as a grafting agent, 0.025 part by weight of KOH as anelectrolyte, and 53.32 parts by weight of distilled water werebatch-added to a nitrogen-substituted reactor, and the temperatureinside the reactor was raised to 70° C. Afterward, 0.03 part by weightof potassium persulfate as an initiator was batch-added to initiatepolymerization, and the polymerization was performed for 2 hours andthen terminated, thereby obtaining a seed (average particle diameter: 54nm).

The average particle diameter of the seed was measured using a Nicomp380 instrument (manufactured by PSS Nicomp) by a dynamic lightscattering method.

<Preparation of Core>

Polymerization was performed for 2.5 hours while continuously adding, tothe seed-containing reactor, a mixture including 43 parts by weight ofbutyl acrylate, 0.5 part by weight of sodium dodecyl sulfate as anemulsifier, 0.1 part by weight of ethylene glycol dimethacrylate as acrosslinking agent, 0.1 part by weight of allyl methacrylate as agrafting agent, 30 parts by weight of distilled water, and 0.05 part byweight of potassium persulfate as an initiator at 70° C. and apredetermined rate. After the continuous addition was terminated,polymerization was further performed for another 1 hour and thenterminated, thereby obtaining a core (average particle diameter: 101nm).

The average particle diameter of the core was measured using a Nicomp380 instrument (manufactured by PSS Nicomp) by a dynamic lightscattering method.

<Preparation of Shell>

Polymerization was performed for 2.5 hours while adding, to thecore-containing reactor, 36 parts by weight of styrene, 15 parts byweight of acrylonitrile, and 39 parts by weight of distilled water andcontinuously adding each of a first mixture including 1.5 parts byweight of potassium rosinate as an emulsifier, 0.1 part by weight oft-dodecyl mercaptan as a molecular weight controlling agent, and 0.04part by weight of t-butylperoxy ethylhexyl carbonate as an initiator anda second mixture including 0.1 part by weight of sodium pyrophosphate,0.12 part by weight of dextrose, and 0.002 part by weight of ferroussulfate as activators at 75° C. and a predetermined rate. After thecontinuous addition was completed, polymerization was further performedat 75° C. for another 1 hour and then terminated by lowering thetemperature inside the reactor to 60° C., thereby preparing a graftcopolymer latex (average particle diameter: 130 nm) including a shell.

The average particle diameter of the graft copolymer latex was measuredusing a Nicomp 380 instrument (manufactured by PSS Nicomp) by a dynamiclight scattering method.

<Preparation of Graft Copolymer Powder>

A graft copolymer powder was prepared in the same manner as inPreparation Example 1.

Preparation Example 3

A 125-ml high-pressure reactor was evacuated and then filled withnitrogen, and 30 ml of toluene was added thereto. Afterward, the reactorwas placed in an appropriate thermostat, 31 mmol of aluminum (III)chloride and then 31 mmol (about 2.67 g) of methyl acrylate were addedto the reactor, and the reactor was maintained for 30 minutes until thereaction temperature was stabilized. Afterward, 0.0031 mmol ofazobisisobutyronitrile (AIBN) in a dissolved state in 5 ml ofchlorobenzene was injected into the reactor. Subsequently,polymerization was performed for 20 hours by filling the reactor withethylene at 35 bar and raising the reaction temperature to 70° C. Afterthe polymerization was completed, the reaction temperature was loweredto room temperature, and ethanol (non-solvent) was then added toprecipitate the prepared copolymer in a solid phase. The solid-phasecopolymer was allowed to settle to remove a supernatant, and theresulting solid-phase copolymer was washed by adding ethanol again andthen allowed to settle to remove a supernatant. To solidify particles inthe remaining solid phase copolymer, water was added thereto, andstirring and filtration were then performed, thereby collecting only acopolymer. The copolymer thus obtained was dried in a vacuum oven at 60°C. for a day.

Meanwhile, the obtained copolymer had a weight-average molecular weightof 104,000 g/mol and included a methyl acrylate unit at 24 wt % and anethylene unit at 76 wt %.

The weight-average molecular weight of the obtained copolymer wasmeasured as a relative value with respect to a standard PS sample by gelpermeation chromatography (GPC, Waters Breeze) using tetrahydrofuran(THF) as an eluate.

EXAMPLES AND COMPARATIVE EXAMPLES

The specifications of components used in Examples and ComparativeExamples are as follows.

(A-1) First graft copolymer: The graft copolymer powder prepared inPreparation Example 1 was used.

(A-2) Second graft copolymer: The graft copolymer powder prepared inPreparation Example 2 was used.

(B-1) First styrene-based copolymer: 98UHM (commercially available fromLG Chem Ltd., α-methylstyrene/acrylonitrile copolymer, weight-averagemolecular weight: 100,000 g/mol) was used.

The weight-average molecular weight was measured as a relative valuewith respect to a standard PS sample by GPC (Waters Breeze) using THF asan eluate.

(B-2) Second styrene-based copolymer: 97HC (commercially available fromLG Chem Ltd., styrene/acrylonitrile copolymer, weight-average molecularweight: 170,000 g/mol) was used.

The weight-average molecular weight was measured as a relative valuewith respect to a standard PS sample by GPC (Waters Breeze) using THF asan eluate.

(C) Olefin-based copolymer: The copolymer prepared in PreparationExample 3 was used.

The above-described components were mixed in contents shown in thefollowing [Table 1] and stirred to prepare thermoplastic resincompositions.

Experimental Example 1

Each of the thermoplastic resin compositions of Examples and ComparativeExamples was put into a twin-screw extruder kneader set at 230° C. toprepare pellets. A physical property of the pellet was evaluated by themethod described below, and results thereof are shown in the following[Table 1].

(1) Melt flow index (g/10 min): measured in accordance with ASTM D1238at 220° C.

Experimental Example 2

The pellet prepared in Experimental Example 1 was injection-molded toprepare a specimen. Physical properties of the specimen were evaluatedby methods described below, and results thereof are shown in thefollowing [Table 1].

(2) Hardness: measured in accordance with ASTM 785.

(3) IZOD impact strength (kg cm/cm): measured in accordance with ASTM256.

(4) Heat deflection temperature (° C.): measured in accordance with ASTMD648.

Experimental Example 3

The pellet prepared in Experimental Example 1 was extruded through afilm extruder to form a 0.3-mm film. Physical properties of the filmwere evaluated by methods described below, and results thereof are shownin the following [Table 1].

(5) Film appearance: determined by evaluating pressure marks and bumpson the film through visual inspection.

x: deformed film, ∘: good, ⊚: excellent

(6) Chemical resistance: evaluated based on the time required for thefilm to start dissolving after the film was immersed in a beakercontaining methyl ethyl ketone for 2 minutes.

x: 20 seconds or less, ∘: more than 40 seconds and less than 100seconds, and ⊚: 100 seconds or more

TABLE 1 Examples Comparative Examples Classification 1 2 3 4 5 1 2 3 4 5(A-1) First 14 19 15 14 17 3 14 14 — 22 graft copolymer (parts byweight) (A-2) Second 7 2 6 7 4 35 7 7 23 — graft copolymer (parts byweight) (B-1) First 15 12 12 15 12 — 79 15 15 15 styrene-based copolymer(B-2) Second 64 67 67 64 67 62 — 64 62 63 styrene-based copolymer (C)Olefin- 0.5 0.5 0.5 0.7 0.5 0.5 0.5 — 0.5 0.5 based copolymer Melt flowindex 10.1 12.4 13 10.3 12.7 7.7 9.9 9 15.8 8.7 Hardness 112.6 112 112.3112 112.1 104 111.9 114 113 112 Impact strength 7.1 7.1 6.7 6.6 6.9 67.9 7.7 4.4 7 Heat deflection 91.3 89.3 89.4 90 89.3 85 98.5 91.5 90.590 temperature Film appearance ⊚ ◯ ◯ ⊚ ◯ X ⊚ ⊚ X X characteristicsChemical ⊚ ⊚ ⊚ ⊚ ⊚ ◯ X X ⊚ X resistance

Referring to Table 1, it can be seen that Example 1 to Example 5 wereexcellent in terms of a melt flow index, hardness, impact strength, filmappearance characteristics, and chemical resistance and also exhibitedhigh heat deflection temperatures.

On the other hand, it can be seen that Comparative Example 1 notincluding a first styrene-based copolymer exhibited significantlydegraded properties in terms of a melt flow index, heat deflectiontemperature, and impact strength compared to Examples and also exhibitedpoor film appearance characteristics.

It can be seen that Comparative Example 2 not including a secondstyrene-based copolymer and Comparative Example 3 not including a thirdcopolymer exhibited significantly degraded properties in terms of a meltflow index and chemical resistance.

It can be seen that Comparative Example 4 not including a first graftcopolymer exhibited significantly degraded impact strength and alsoexhibited poor film appearance characteristics.

It can be seen that Comparative Example 5 not including a second graftcopolymer exhibited poor chemical resistance and poor film appearancecharacteristics.

It can be predicted from these results that only when all of thecomponents according to the present invention are included, athermoplastic resin molded article excellent in all of processability,hardness, impact resistance, heat resistance, chemical resistance, andappearance characteristics can be prepared.

The invention claimed is:
 1. A thermoplastic resin compositioncomprising: a first graft copolymer including a C₄ to C₁₀ alkyl(meth)acrylate-based monomer unit, a C₁ to C₃ alkyl-substitutedstyrene-based monomer unit, and a vinyl cyan-based monomer unit; asecond graft copolymer including a C₄ to C₁₀ alkyl (meth)acrylate-basedmonomer unit, an alkyl-unsubstituted styrene-based monomer unit, and avinyl cyan-based monomer unit; a first styrene-based copolymer includinga C₁ to C₃ alkyl-substituted styrene-based monomer unit and a vinylcyan-based monomer unit; a second styrene-based copolymer including analkyl-unsubstituted styrene-based monomer unit and a vinyl cyan-basedmonomer unit; and an olefin-based copolymer including a C₁ to C₃ alkyl(meth)acrylate-based monomer unit.
 2. The thermoplastic resincomposition of claim 1, wherein the first graft copolymer furtherincludes an alkyl-unsubstituted styrene-based monomer unit.
 3. Thethermoplastic resin composition of claim 1, wherein the first graftcopolymer and the second graft copolymer have cores having mutuallydifferent average particle diameters.
 4. The thermoplastic resincomposition of claim 1, wherein the first graft copolymer has a corehaving an average particle diameter of 300 to 500 nm.
 5. Thethermoplastic resin composition of claim 1, wherein the second graftcopolymer has a core having an average particle diameter of 50 to 150nm.
 6. The thermoplastic resin composition of claim 1, wherein theolefin-based copolymer includes a C₂ to C₄ olefin-based monomer unit andthe C₁ to C₃ alkyl (meth)acrylate-based monomer unit in a weight ratioof 85:15 to 65:35.
 7. The thermoplastic resin composition of claim 1,wherein the olefin-based copolymer has a weight-average molecular weightof 50,000 to 200,000 g/mol.
 8. The thermoplastic resin composition ofclaim 1, which includes, with respect to 100 parts by weight of the sumof the first graft copolymer, the second graft copolymer, the firststyrene-based copolymer, and the second styrene-based copolymer, 0.01 to2 parts by weight of the olefin-based copolymer.
 9. The thermoplasticresin composition of claim 1, which includes, with respect to 100 partsby weight of the sum of the first graft copolymer, the second graftcopolymer, the first styrene-based copolymer, and the secondstyrene-based copolymer, 0.5 to 1 part by weight of the olefin-basedcopolymer.
 10. The thermoplastic resin composition of claim 1, whereinthe sum of the content of the first graft copolymer and the content ofthe second graft copolymer is 10 to 35 parts by weight with respect to100 parts by weight of the sum of the first graft copolymer, the secondgraft copolymer, the first styrene-based copolymer, and the secondstyrene-based copolymer.
 11. The thermoplastic resin composition ofclaim 10, wherein a weight ratio of the first graft copolymer and thesecond graft copolymer is 1.5:1 to 10:1.
 12. The thermoplastic resincomposition of claim 1, wherein the sum of the content of the firststyrene-based copolymer and the content of the second styrene-basedcopolymer is 65 to 90 parts by weight with respect to 100 parts byweight of the sum of the first graft copolymer, the second graftcopolymer, the first styrene-based copolymer, and the secondstyrene-based copolymer.
 13. The thermoplastic resin composition ofclaim 12, wherein the first styrene-based copolymer is included in anamount of 14 to 20 parts by weight with respect to 100 parts by weightof the sum of the first graft copolymer, the second graft copolymer, thefirst styrene-based copolymer, and the second styrene-based copolymer.14. The thermoplastic resin composition of claim 1, which includes, withrespect to 100 parts by weight of the sum of the first graft copolymer,the second graft copolymer, the first styrene-based copolymer, and thesecond styrene-based copolymer: 5 to 30 parts by weight of the firstgraft copolymer; 0.1 to 15 parts by weight of the second graftcopolymer; 2 to 25 parts by weight of the first styrene-based copolymer;and 50 to 80 parts by weight of the second styrene-based copolymer. 15.The thermoplastic resin composition of claim 1, which includes, withrespect to 100 parts by weight of the sum of the first graft copolymer,the second graft copolymer, the first styrene-based copolymer, and thesecond styrene-based copolymer: 10 to 15 parts by weight of the firstgraft copolymer; 5 to 8 parts by weight of the second graft copolymer;14 to 16 parts by weight of the first styrene-based copolymer; 62 to 66parts by weight of the second styrene-based copolymer; and 0.3 to 0.6part by weight of the olefin-based copolymer.